This invention relates to a trim adjusting system for a jet propulsion boat and more particularly to an improved hull configuration for a jet boat, an apparatus for adjusting the trim of a boat and a control for the trim adjustment.
A type of watercraft that has become very popular is known as a "personal watercraft." Such personal watercraft are designed to be operated by a rider and will accommodate a relatively small number of passengers. Quite frequently, these watercraft are propelled by jet propulsion units. This type of watercraft is also very sporting in nature and the occupants generally wear swimming suits when enjoying such watercraft.
By their very nature, these watercraft are quite small. One problem with watercraft of such small size, particularly those having relatively short lengths, is that they evidence a tendency to porpoise. Although the porpoising effect can be reduced by increasing the length of the hull, the increased hull length gives rise to added drag and loss in performance.
It is, therefore, a principle object of this invention to provide an improved hull for a small watercraft wherein the effect of porpoising can be decreased without increasing the drag of the hull.
One way in which the porpoising effect can be eliminated without increasing the drag is to employ a step at the rear of the hull. By employing such step, the effective length of the hull can be increased while the drag is decreased. With these arrangements, however, the effect of the step is generally fixed and this may not always be desirable.
It is, therefore a still further object of this invention to provide an improved stepped watercraft hull having an apparatus for adjusting the trim of the hull and the effectiveness of the step.
One way in which the trim of a watercraft can be adjusted if powered by a jet propulsion unit is by pivoting the discharge nozzle about a horizontally disposed transversely extending axis. Upon such pivoting, the trim of the watercraft can be adjusted. This feature is particularly advantageous when utilized with stepped hulls. However, it is desirable to provide a simple and easy way in which the trim can be adjusted by the operator and which will not necessitate his taking his hands off of the steering control for the watercraft to effect trim adjustment.
It is, therefore, a still further object of this invention to provide an improved trim adjustment mechanism for a watercraft.